\documentclass{article}
\usepackage[
a3paper,landscape,
left=0cm,right=0cm,
top=0cm,bottom=0cm
]{geometry}
\usepackage{graphicx}

\begin{document}
\hspace{0.471\textwidth}%
\IfFileExists{../example/demo.pdf}{
    \includegraphics[page=1,]{../example/demo.pdf}
    }{
        \IfFileExists{../example/temp/demo.pdf}{
            \includegraphics[page=1,]{../example/temp/demo.pdf}
        }{
            Plese choose the right picture place!!!
        }
    }
\end{document}
